Three dimensional (3D) optical interconnects for high-speed computing offer many advantages over metal interconnects. For example, 3D optical interconnects provide high-speed transmission with low crosstalk independent of data rates. Currently, there are two major types of 3D optical interconnects: free-space optical interconnects and physical optical interconnects.
Free-space optical interconnects exploit free space (e.g., lenses and holograms in free space). Free-space optical interconnects, by virtue of their inherent parallelism, exhibit high data bandwidth, small size and power requirement, and relative freedom from mutual interference of signals. With these features, free-space optical interconnects show great promise in replacing metal interconnects to solve communication problems.
Physical optical interconnects, on the other hand, have a relatively low interconnection density, and lack of bending or looping flexibility. The physical optical interconnect can also suffer from crosstalk between adjacent optical waveguide structures, and can exhibit severe coupling losses.